Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session CCC08: V: General Physics VI |
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Chair: Kaveh Delfanazari, University of Glasgow Room: Virtual Room 8 |
Wednesday, March 22, 2023 3:00PM - 3:12PM |
CCC08.00001: Enzyme Activity and Diffusivity of Alkaline Phosphatase Functionalized nanoparticles. Anas Alhasanat, Anand Yethiraj Anas Alhasanat* and Anand Yethiraj*. |
Wednesday, March 22, 2023 3:12PM - 3:24PM |
CCC08.00002: Properties of vibronic excitations of SnV centers in diamond Viatcheslav V Dobrovitski, Xinru Tang, Fenglei Gu, Johannes Borregaard Negatively charged tin-vacancy (SnV) defects in diamond hold much potential for quantum communication and modular quantum computation. Almost 40% of the photons emitted by an SnV center are entangled to its spin, and can be used for entangling distant SnV spins. SnV spin qubits can operate at relatively high temperatures of 1-2 K, and are robust to electric fields. However, detailed understanding of many physical aspects of SnV centers is still lacking. |
Wednesday, March 22, 2023 3:24PM - 3:36PM |
CCC08.00003: Optimized Normalizing Flow for Molecular Discovery Jarvis Loh Conventional materials design and discovery involves human domain knowledge to propose candidate materials, and subsequently for their synthesis and testing. This entire process is costly and time-consuming, therefore limiting the throughput and diversity of materials that are explored. Machine learning using generative models provides a promising solution. In this study, we built a normalizing flow (NF), optimized to allow quick and accurate discovery of novel small molecules. Firstly, SELFIES representations were converted from the SMILES representations of molecules randomly selected from the QM7, QM8, QM9 and ChemBL molecular datasets. Sampling molecules from more than one dataset increases their variety in the training data so that generalizability of the model is improved. Next, molecules were generated from a NF, while the hyperparameters of the NF, including the composition of the flow such as the number of hidden units in the autoregressive network, the number of NF layers, learning rate, and batch size, were optimized by multi-objective Bayesian optimization (MOBO) to minimize the mean divergences (Kullback-Leibler, Wasserstein) between the generated and training molecules. Molecules subsequently re-sampled from the target distribution of the NF with the optimal hyperparameters were screened to eliminate those with low similarity compared with the training molecules. The chemical validity, novelty, uniqueness, and internal diversity of the generated molecules were verified, and their synthetic accessibility score (SA score) and synthetic complexity score (SCScore) distributions were compared against those of the training molecules. Finally, the NF model was benchmarked using MOSES datasets to evaluate its quality. |
Wednesday, March 22, 2023 3:36PM - 3:48PM |
CCC08.00004: The drying of isotropic and anisotropic colloids under confinement DILLIP KUMAR MOHAPATRA, Madivala G. Basavaraj, Dillip K. Satapathy, Anand Yethiraj Drying colloidal dispersions have been used extensively as examples of collective transport processes, particularly in fixed (sessile) drops. Much less attention, however, has been paid to the drying of droplets in the capillary liquid bridge configuration. Such confined drying is relevant in medical and industrial applications. We study the evaporation dynamics and deposition pattern of a colloidal dispersion containing particles of different shapes and sizes in restricted geometry. The effect of confinement spacing, particle size and shape, concentration, and the presence of an external field on the drying deposition pattern was investigated under ambient conditions. The drying deposition pattern of colloids containing nanoellipsoids results in a stick-slip pattern at high confinement spacing and a labyrinthine pattern at low confinement spacing. However, dispersions containing microparticles such as microellipsoids, cubes, and peanuts leave a uniform deposit at high confinement spacing and labyrinthine patterns at low confinement spacing after solvent evaporation. We measure the dependence, on concentration (Cs) and confinement spacing (hc), of a characteristic length scale (Λc), which represents the spacing between the branched patterns, to elucidate the origin, and dependence on particle shape, of the labyrinthine patterns. |
Wednesday, March 22, 2023 3:48PM - 4:00PM |
CCC08.00005: Synthesis and Size Dependence of Strongly Correlated Ferrite Nano-Objects Frank M Abel, Eduardo L Correa, Thinh Q Bui, Adam Biacchi, Michael J Donahue, Solomon I Woods, Angela R Hight Walker, Cindi L Dennis Recent results have shown that high quality ferrite particles functionalized with oleic acid can produce significant gains in magnetic particle imaging (MPI) signal and imaging resolution when stimulated with an AC field with an amplitude greater than 10 mT.1 The proposed mechanism is the formation of linear chains due to strongly correlated inter-particle interactions and is characterized by a square AC hysteresis loop, enhanced MPI resolution, and a large change in MPI signal at a threshold field. Here we have synthesized ferrite particles from approximately 15 nm to 25 nm by a one-step colloidal method. The particles were physically characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and dynamic light scattering. The strongly correlated nature of the particles was investigated by drive field dependent magnetic particle spectroscopy (MPS) measurements at 5 kHz frequency. Particles with a mean size of about 19 nm and larger show distinct features of a strongly correlated system: a threshold field where the MPI signal sharply increases and nearly square AC hysteresis loops at fields above the threshold regime. The 15 nm particles do not clearly show this behavior. The results suggest that a minimum critical size is required for the strongly correlated behavior to occur in ferrite particles. |
Wednesday, March 22, 2023 4:00PM - 4:12PM |
CCC08.00006: Performing a Digital Nucleic Acid Test in a Nanofluidic Device with Pneumatic Confinement Control Seyed Imman Isaac Hosseini, Walter W Reisner, Sara Mahshid, Xavier Capaldi, Seyed Vahid Hamidi Nano/microfluidic-based nucleic acid tests have been proposed as a rapid and reliable diagnostic technology. The two key steps for many of these tests are target nucleic acid (NA) surface immobilization followed by an enzymatic reaction on the captured NAs to detect the presence of a disease associated sequence. NA capture within a geometrically confined volume is an attractive alternative to NA surface immobilization that eliminates the need for sample pre-treatment (e.g. label-based methods such as lateral flow assays) or use of external actuators (e.g dielectrophoresis) that are required for most nano/microfluidic-based NA tests. However, geometrically confined spaces hinder sample loading while making it challenging to capture, subsequently retain and simultaneously expose target NAs to required enzymes. Here, using a nanofluidic device that features real-time confinement control via pneumatic actuation of a thin membrane lid, we demonstrate loading of digital nanocavities by target NAs and exposure of target NAs to required enzymes/co-factors while the NAs are retained. In particular, as proof of principle, we amplified single-stranded DNAs (M13mp18 plasmid vector) in an array of nanocavities via two isothermal amplification approaches (loop-mediated isothermal amplification and rolling cyclic amplification). |
Wednesday, March 22, 2023 4:12PM - 4:24PM |
CCC08.00007: Temperature dependent study of charge-state dynamics of nitrogen-vacancy center in diamond SAGAR CHOWDHURY, Anand Patel, Ashutosh Rathi, Vidya Praveen Bhallamudi Negatively charged nitrogen-vacancy centers in diamond have drawn intense research interest in recent years. Charge-state conversion of the negatively charged state to the neutral state can be a boon for electrical control of NV centers[1] but also lead to loss of the negatively charged state crucial for sensing and other quantum technologies[2]. Here we aim to report on our results in analyzing temperature-dependent fluorescence spectra of NV ensembles as a function of laser power and magnetic field to shed more light on the charge-state dynamics of NV centers. |
Wednesday, March 22, 2023 4:24PM - 4:36PM |
CCC08.00008: Achieving a molecular level control on surface cation segregation in double perovskite NdBaCo2O5+δ using dopants and strain effects Jyotsana Kala, Uzma Anjum, Brajesh K Mani, M Ali Haider The increasing demand of clean, renewable energy is leading research interest towards solid oxide fuel cells (SOFCs). AA′Co2O5+δ (A= rare earth ion, and A′= alkaline earth ion) double perovskite oxides have been proposed as potential candidate for intermediate temperature SOFC cathodes [1]. Density functional and molecular dynamics theory-based simulations are performed to study the electrocatalytic and magnetic behavior of NdBaCo2O5+δ. Oxygen vacancy formation energies of Ba/O plane observed to be highest among different layers along (001) direction. Magnetic properties study depicts an opposite correlation between magnetic moment and oxygen vacancy formation energies. Study of different surface terminations shows Ba/Co as a stable termination. Ba cation segregation is observed to affect the surface stability of material [2,3]. Here, we put forward strain and dopant effect strategies to control and suppress the Ba cation segregation. Strain engineering offer tailoring the electrocatalytic and magnetic properties, thus opening up a pathway to improve the performance. NdBa0.75Sr0.25Co2O5+δ shows more Sr cation segregation [4]. Sr and Ca doping at A′-site resulted in the suppression of Ba cation segregation also total A′-site cation segregation. Present work focusses on understanding underlying physics of different key driving forces, suppression techniques of A′-site cation segregation in NdBaCo2O5+δ. |
Wednesday, March 22, 2023 4:36PM - 4:48PM |
CCC08.00009: Effect of substrate and growth method on vanadium dioxide thin films by RF magnetron sputtering Adam S Christensen, Agham Posadas, Brian T Zutter, Albert A Talin, Alexander A Demkov We explore two methods of vanadium dioxide (VO2) thin film deposition using off-axis RF magnetron sputtering on (100)- and (111)-oriented yttria-stabilized zirconia (YSZ): reactive sputtering of vanadium in an oxygen environment and sputtering of vanadium metal followed by oxidation to VO2. The reactive sputtering process on both substrate orientations yields VO2 (B), a metastable phase epitaxially stabilized by the YSZ surface. The metal sputtering and oxidation process on YSZ produces mainly the stable M1 phase of VO2. Using this method, we achieve thin films of (010)-oriented VO2 (M1) exhibiting a metal-insulator transition with a resistance ratio on the order of 103. |
Wednesday, March 22, 2023 4:48PM - 5:00PM |
CCC08.00010: Raman signatures of spin-phonon coupling and quadratic band touching state in Pyrochlore Iridates (Sm1-xBix)2Ir2O7 Rosalin Mohanty The 5d transition metal oxides stand at the crossroad of strongly correlated systems where the SOC and the coulomb interaction compete at the same energy scale. In 5d Iridates this is further enhanced by the crystal field interaction that splits the t2g orbital and leaves the system in a low spin state (jeff=1/2). Among the iridates pyrochlore Iridates A2Ir2O7 (A=Y, Bi, and rare earth elements) have attracted much scientific attention as they potentially show various exotic phenomena and topologically non-trivial ground states. The SOC dominant Dzyaloshinskii-Moriya interaction competes with the inherent geometric spin-frustration giving rise to a non-co-linear “all-in or all-out” (AIAO) antiferromagnetically ordered ground state with broken time-reversal symmetry. The delicate relation between metal-insulator transition (MIT) and AIAO magnetic ordering in the 5d-pyrochlore iridates has provided a fated goal to search for the fingerprints of exotic states of matter in these geometrically frustrated systems. Here we use Raman spectroscopy to investigate the temperature dependence of phonons and magnetic as well as electronic background in (Sm1-xBix)2Ir2O7 samples. While both Bi2Ir2O7 and Sm2Ir2O7 stabilize in pyrochlore structure: the former is a correlated metal, and the latter is a Weyl Semi-metal (WSM) candidate with concomitant MIT near ~120 K. A strong spin-phonon coupling, and magnetic-order induced phonon renormalization is observed near magnetic transition temperature TN for samples with x≤0.035. Phonon anomalies at a scaling temperature much lower than TN are observed (for x≤0.02) and are possibly correlated with a crossover to the WSM state. An underlying broad scattering continuum attributed to pronounced spin-spin correlation is observed below TN for pure Sm2Ir2O7. We observe signatures of quadratic band touching (QBT) in x=0.05 and 0.10 samples in terms of a broad electronic continuum at low temperatures corroborating the inferences from transport measurements. |
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